The present invention relates to a lamp system with an electronic ballast circuit. More specifically, the present invention pertains to a lamp system with an electronic ballast circuit capable of supplying the power consumed at the lamp in conformity with the intention of the designer.
In general, a lamp system with an electronic ballast circuit performs an open loop control in order to generate a separate excitation frequency. During the open loop control, the separate excitation frequency for driving the LC (Inductor-Capacitor) resonance terminal of the lamp is varied due to errors of the time capacitor, as well as, the inductor or capacitor of the LC resonance terminal. As a result of this frequency variation the lamp may experience difficulty turning on and/or the brightness may vary, such that it is greater or less than the intended designed value.
It is an object of the present invention to solve the problems related to the prior art and to provide a lamp system with an electronic ballast circuit that performs a feedback closed control to detect the current flowing through the lamp and to compare the detected current to a reference voltage. In this regard, the lamp system controls the variation of the frequency occurring due to the errors of the elements and performs normal operational lamp control, as well as a soft start function and a soft dimming function.
To achieve the above object of the present invention, the lamp system with an electronic ballast circuit generates a reference voltage according to the user""s on/off and illuminating directions. Once the reference voltage is generated it is compared to a voltage obtained by feeding back the current flowing through the lamp. The comparison thereby controls the magnitude of the current flowing through the lamp.
In one aspect of the present invention, there is provided a lamp system including a power supply, a current controller, a lamp section, and a feedback section.
The power supply is provided to supply power to the entire system, and the current controller includes first and second switches. The current controller is coupled to the on/off periods of the first and second switches to control the magnitude of a lamp driving current.
The lamp section is operated using the current supplied by the current controller. The feedback section generates a feedback voltage using the current flowing through the lamp section, and compares the feedback voltage to a reference voltage to determine whether the current input to the lamp section has a magnitude of an overcurrent, an undercurrent, or a normal current. Thus, the feedback section can control the on/off periods of the first and second switches.
In another aspect of the present invention, there is provided a ballast circuit including an undervoltage protector, a soft starter, a dimming controller, a feedback section, a frequency controller, and a switch driver.
The undervoltage protector prevents a malfunction of the entire system, and generates an initial operating signal of the entire system upon receiving a voltage of less than the voltage capable of operating the entire system.
The soft starter gradually increases a soft start voltage to a predetermined level to proceed with a start-up of the lamp upon receiving the initial operating signal from the undervoltage protector.
The dimming controller permits a gradual increase in voltage even when an externally input dimming signal is changed in order to regulate the light intensity.
The feedback section compares a feedback voltage generated based on the magnitude of the current flowing through the lamp to a reference voltage generated based on the output signals from the soft starter and the dimming controller. As a result of the comparison the feedback section provides normal operation to the lamp, as well as, soft start and soft dimming function capability. In addition, the feedback section determines whether the current flowing through the lamp is an overcurrent, an undercurrent, or a normal current.
The frequency controller generates first and second frequencies for regulating the magnitude of the current input to the lamp based on a received signal from the feedback voltage. The frequency controller generates the first frequency when the feedback voltage is greater than the reference voltage and the second frequency is [being] generated when the feedback voltage is less than the reference voltage.
The switch driver is coupled to the first and second frequencies to control the on/off state of the switch of the current controller.
In still another aspect of the present invention, there is provided a lamp system including a power-factor compensator, a current controller, a lamp section, a ballast, and a dimming voltage controller.
The power-factor compensator rectifies AC power and improves the power factor of the rectified AC power to increase the effective power supplied to the entire system.
The current controller includes first and second switches. The current controller is coupled to the on/off periods of the first and second switches for controlling the magnitude of a lamp driving current from the power-factor compensator.
The lamp section includes a resonance circuit composed of a resistor, an inductor and a capacitor, and it emits light under a current from the current controller.
The ballast forms a feedback voltage using a current flowing through the lamp section during operation of the lamp including during soft start and dimming control periods, and compares the feedback voltage to a reference voltage to determine whether the current input to the lamp section is an overcurrent, an undercurrent, or a normal current. Thus the ballast controls the on/off periods of the first and second switches.
The dimming voltage controller generates a dimming signal to the ballast to perform the dimming control of the lamp.